Pentagonal building block



FIG. 1 is a perspective view of a pentagonal building block, showing our new design;

FIG. 2 is a top plan view thereof, showing the vertical and horizontal symmetry of the design;

FIG. 3 is a bottom plan view thereof, which is a mirror image of the front elevation view;

FIG. 4 is a front elevation view thereof;

FIG. 5 is a back elevation view thereof, which because of the vertical and horizontal symmetry of the design, is a mirror image of the front elevation view;

FIG. 6 is a left side elevation view thereof, which because of the vertical and horizontal symmetry of the design, is a rotation from the front elevation view; and,

FIG. 7 is a right side elevation view thereof, which because of the vertical and horizontal symmetry of the design, is a mirror image of the left side elevation view. 

CLAIM The ornamental design for a pentagonal building block, as shown and described. 